Here i want to show you a nice sounding and easy to play Quick Change Blues tune.

Standard 12 bar blues

"The basic 12-bar lyric framework of a blues composition is reflected by a standard harmonic progression of 12 bars in a 4/4 time signature. The blues chords associated to a twelve-bar blues are typically a set of three different chords played over a 12-bar scheme." - Wikipedia. In this tune the chords are A7, D7 and E7.

Quick Change Blues

The change in quick change blues happens in bar 2. This progression, so called because of the change from the I(A7) to the IV(D7) chord which happens so early in the progression, is identical to the traditional 12 bar blues progression with the exception of bar 2. In quick change blues, bar 2 is the IV(D7) chord instead of the I(A7) chord.